Foundation pit design, designers are facing the biggest problem is that the earth pressure calculation, between different design codes for the calculation of earth pressure have great differences caused by structural design is not accurate enough, unified. Moreover, because the earth pressure is influenced by many factors, its size is not static, and it is a great hidden danger to the safety of foundation pit support. The excavation of soil nailing for, considering the effect on the earth pressure caused by the excavation of foundation pit in the process of displacement of excavation and soil nail support retaining structure deformation, re defined by considering the horizontal displacement of foundation pit and deformation of support structure of earth pressure calculation and distribution form and combined with the practical engineering to verify its applicability in engineering.